Calculating Offline Time

[Astram]

How would I calculate offline time? I mean how can I tell time, like in 2hrs a player would be unjailed even if he/she is offline. (I'm currently not concerned on the "setlevel2();") for when the players unjailed offline. But, I need a way to calculate time while offline. So it invokes something in 2hrs if the player is offline or not. And please explain the way simply. As timevar2 gets me confused.